The prior art in the field of flat panel display devices includes: Liquid Crystal Displays (LCD), Cathode Ray Tube (CRT) displays, pen/stylus input screen means, and fiberoptic faceplates. There is a great amount of prior art in LCD and CRT devices and systems. There is a fair amount of prior art in pen or stylus position input encoding means, which is defined as apparatus used to determine (encode) the position of a stylus or pen as it is moved over an area by the hand of a person. Thus, when a person writes, draws or sketches onto or over and an active area, a signal is generated representing its position repeatedly as the pen is moved. Typically, these devices make use of a electromagnetic sensors or emitters that either cover the front of a display screen or placed behind the screen. Prior art combinations of pen input devices with display devices include U.S. Pat. No. 4,361,725 of Dagnelie, which discloses a CRT with a roughly transparent grid placed onto a conventional CRT glass faceplate. Prior art in the combination of touch panels to a displays include Japanese Patent 59-184925 of Sugiyama, which discloses a touch screen placed over a CRT. U.S. Pat. No. 4,911,536 of Ditzik discloses a graphic tablet encoding means placed over an projection screen of a non-direct view projection display device. Each of these prior art combinations suffer from several shortcomings, such as the parallax effect, large number of parts, and/or high cost.
Prior art in fiberoptic (FO) faceplates involve placing them onto display devices for the purpose of optical coupling the display screen to an optical system, or using them in high brightness direct view displays. CRTs have been manufactured with fiberoptic plates, which focuses and relays the image from the CRT to a light valve or large screen projection system. U.S. Pat. No. 4,591,232 of Jeskey disclosed fiberoptic CRT faceplates that have light absorbing black fibers dispersed throughout the bundle to reduce "halation" or "ballooning" of the image. U.S. Pat. No. 4,573,082 of Jeskey disclosed a similar CRT fiberoptic faceplate for optical transfer of an enhanced image to a projection screen. In addition, European Patent 0122829 of Rover et. al. disclosed a fiberplate to act as an optical filter in order to provide optimum visibility of a display device under a variety of ambient viewing conditions. The primary shortcoming of the these piror art display devices is that they do not disclose or anticipate pen/stylus input means integrated with a display. This puts such display devices at a severe disadvantage in the highly interactive computer, display, and PDA markets.
There is prior art in placing stylus digitizers onto display devices. For example, U.S. Pat. No. 3,671,668 of Reiffel discloses a CRT having a standard glass faceplate with a transparent spatial signal generator placed onto it and separated by an air gap. U.S. Pat. No. 4,723,836 of Kono and Inoue disclosed an electromagnetic opaque digitizer tablet placed behind a LCD panel. However, in each of these cases, there exists a top glass substrate, a polarizer and other components between the display image and the viewer's eyes. The thickness of these components causes an undesirable effect of parallax. The parallax effect is defined as the viewable gap or distance between the pen/stylus tip placed onto the screen and the actual viewed image. The above display devices and pen/stylus input device combinations have parallax. This is very annoying and objectionable effect to the user who is trying to write or draw onto the display screen. It is especially a problem with CRT displays, which may have faceplates roughly 0.5-0.85 inch thick.
U.S. Pat. No. 4,873,398 of Hubby discloses means to reduce the parallax effect by introducing a lens or lens arrays placed between a LCD panel and a transparent digitizer means. Hubby's lens or array projects the image from the display through the digitizer plate to a separate rear projection screen. This may reduce the parallax effect somewhat, but it has several shortcomings. First, the lens array will have significant light loss from lens to lens cross transmission. This will cause a low contrast image. Secondly, the disclosed projection screen must have a thickness; therefore, the screen itself will cause some parallax. Finally, with the prior art components, the displayed image will be distorted by digitizer layer and lens array layers. U.S. Pat. No. 4,943,348 of Ibamoto et al disclose two or more micro lens arrays placed between a LCD and a protective glass or pen tablet means. However, Ibamoto's arrangement introduces unnecessary complexity by having two or more lens arrays to register with respect to each other, for providing an erect image. Ibamoto's fails to realize that an erect image on a pixel bases is not necessary in display devices. The above embodiments suffer from an overly complex design with a high parts count and high associated cost.
Besides the parallax effect, another shortcoming of prior art display devices and pen display combinations is optical glare from the front surface of the screen. Prior art solutions for screen glare involve special coating(s) or frosting the front surface. A disadvantage of placing anti-glare optical coatings onto a display screen is that it adds significant cost to the display. Both of the above anti-glare techniques cause some degradation of the displayed image, due to light scattering and light absorption of the material. These image degradation effects are caused by the various coatings, plates or films placed between the image material (LC or phosphor) and the user's eyes. These shortcoming cause serious ergonomic problems, especially when a person is trying to point, write and/or draw onto the display screen.
The inventions of the applicant overcomes each of the above prior art shortcomings and disadvantages by tightly integrating one or more fiberoptic faceplates to a direct view display device. A first faceplate may be manufactured as a part of the display device. A second faceplate may form a substrate for a pen/stylus input sensor/emitter means. When the second faceplate is placed against the first with very little or no gap, the two faceplates will appear as one plate, of zero thickness, to the viewer. This embodiment will virtually eliminate any parallax effect for the viewer. In addition, there will be less front surface glare and a wider viewing angle. In LCD display panels, a fiberoptic faceplate will provide for a brighter image in darken ambient room lighting conditions. These advantages over the prior art will insure a wider acceptance of the display device in the highly interactive computer, communications, and entertainment markets.
Certain flat panel display devices, such as Liquid Crystal Displays (LCD), may require a backlight for better viewability. A number a backlight technologies are known to provide a relatively uniform light to the back of display panels. Prior art in backlights include electro luminescent, fluorescent, incandescent, and LED light sources. A number of light guide devices have been used to apply light to the rear of the display panel, using various fiber, glass, and plastic optical guides. However, several problems arise when the display must be viewed under sunlight, twilight, or night conditions. Each of these viewing conditions require different backlighting designs. The new multiple backlight invention described herein solves these problems by providing a simple way of using multiple light sources and integrating their light to the rear of an LCD panel.